1. Field of the Invention
This invention relates to lasers, and more particularly it relates to pumping methods and apparatus for laser-pumped lasers wherein the pumping laser beam is caused to effectively scan the laser medium.
2. Description of the Prior Art Including Prior Art Statement
Certain laser-pumped lasers utilize laser media in which active ions or molecules are embedded in a solid matrix. One example of such a laser is a plastic/dye laser wherein a plastic matrix is impregnated with an organic laser dye. A further example is a Nd:glass laser wherein neodymium ions are embedded in a glass body.
In lasers of the foregoing type, under high average power pumping conditions the laser medium may experience sufficient heating to produce substantial refractive index gradients. In the case of plastic/dye lasers, decomposition of the dye and/or melting of the plastic may occur as well. As a result of these effects, the beam quality (product of the beam divergence and beam diameter) of the generated laser beam, the average power output and the operating life of the laser are significantly limited.
In the prior art, reduced pump flux loading on a laser medium in the form of a dye-bearing plastic disk has been obtained by rotating the disk about an axis passing through the center of the disk and parallel to a stationary pump beam. The pump beam is thus caused to effectively scan an annular region of the disk at a constant radial distance from the center of the disk. Further details concerning the aforementioned rotating disk arrangement may be found in the paper by David L. Hecht et al, "Dye Lasers With Ultrafast Transverse Flow", IEEE Journal of Quantum Electronics, Vol. QE-8, No. 1 (Jan. 1972), pp. 15-19.
Although the aforedescribed rotating disk dye laser is able to expose substantially more disk material to the pump beam than with a stationary disk, the annular region of the disk on which the pump beam impinges covers only a small fraction of the disk surface. Therefore, only a small portion of the disk volume is actually utilized, and the beam quality, average power output and operating life of the laser are still limited.